Functionally substituted Schiff bases in reduction reactions

Article abstract of DOI:10.1134/S1070428013020073

Functionally substituted Schiff bases obtained by the condensation of nitroaniline, pyrimidinylaminoaniline, 5-aminoquinoline, 5-aminoquinaldine derivatives with 4-methylformylbenzoate were studied in the reactions of sodium borohydride with acidic activators, hydrazine hydrate in the presence of Raney nickel, Raney alloy in the presence of potassium hydroxide. By the reduction of azomethines new benzyl derivatives of aniline, quinolylamine, arylaminopyrimidine, and phenylenediamine were obtained.

Full text of DOI:10.1134/S1070428013020073

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2013, Vol. 49, No. 2, pp. 212−220. © Pleiades Publishing, Ltd., 2013.
Original English Text © E.V. Koroleva, K.N. Gusak, Zh.V. Ignatovich, A. L. Ermolinskaya, 2013, published in Zhurnal Organicheskoi Khimii, 2013, Vol. 49,
No. 2, pp. 223−231.
Functionally Substituted Schiff Bases in Reduction Reactions
E. V. Koroleva, K. N. Gusak, Zh. V. Ignatovich, and A. L. Ermolinskaya
Institute of Chemistry of New Materials, National Academy of Sciences of Belarus,
Minsk, 220141 Belarus
e-mail: evk@ichnm.basnet.by
Received June 19, 2012
Abstract—FunctionallysubstitutedSchiffbasesobtainedbythecondensationofnitroaniline,pyrimidinylaminoaniline,
5-aminoquinoline, 5-aminoquinaldine derivatives with 4-methylformylbenzoate were studied in the reactions of
sodium borohydride with acidic activators, hydrazine hydrate in the presence of Raney nickel, Raney alloy in the
presence of potassium hydroxide. By the reduction of azomethines new benzyl derivatives of aniline, quinolylamine,
arylaminopyrimidine, and phenylenediamine were obtained.
DOI: 10.1134/S1070428013020073
Schiff base due to the presence in the molecule of
the reactive C=N bond are widely used in the organic
synthesis [1-3]. Particularly noteworthy are the reduction
reaction of azomethines opening the way to the synthesis
of unsymmetrical secondary amines, compounds with a
high potential of practical applications [4, 5].
tion methyl 4-[(2-methyl-1,2,3,4-tetrahydroquinolin-5-
ylamino)methyl]benzoate [6]. The product of the selective
reduction of the azomethine bond in imine molecule XV,
methyl 4-[(2-methylquinolin-5-ylamino)methyl] benzoate
(XXII) was obtained at 0–5°C in a 76% yield.
Synthesis of benzylamines XVI–XIX was also car-
ried out by reductive alkylation of amines I–IV with
4-methoxycarbonylbenzaldehyde (VIII) in the system
NaBH4–AcOH. The yield of reaction products was
somewhat lower (52-80%) than in the reduction of azo-
methines obviously due to incomplete conversion of the
reagents into the intermediate imine. According to TLC,
the traces of the initial amine and aldehyde were present
in the crude product regardless of the temperature and
the reaction time.
In extension of the research on the reductive trans-
formations of azomethines based on derivatives of
nitro- and pyrimidinyilaminoaniline, 5 aminoquinoline,
5 aminoquinaldine [6] this paper presents results of a
study of transformations of Schiff bases obtained by
condensation of substituted anilines [4-methyl-3-nitro-(
I), 2-trifluoromethyl-4-nitro- (II), 2-methyl-4-nitro- (III),
2-methyl-5-nitro- (IV), 2-methyl-3-[(pyridin-3-yl) pyrim-
idin-2-yl]amino- (V) anilines] and 5-aminoquinolines VI,
VII with methyl 4-formylbenzoate (VIII). Synthesized by
the method [7] imines IX-XV were studied in the reac-
tions with sodium borohydride in the presence of acetic
acid and boric acid as activators, with Raney alloy in the
presence of potassium hydroxide, and with hydrazine
hydrate in the presence of Raney nickel.
The most effective reducers of the nitro group to the
amino group in compounds XVI, XVIII, XIX to give the
corresponding aminobenzyl derivatives XXIII–XXVI
turned out to be Raney alloy in the persence of KOH at
heating the reaction mixture to 55°C, and also hydrazine
hydrate–Raney nickel [6] .Aminobenzylanilines XXIII-
XXV were obtained in the preparative yield of 62–80%.
The reduction of imines of the aniline series IX–XIII
and methyl 4-[(5-quinolinylimino) methyl] benzoate (XIV)
with sodium borohydride in the presence of acetic acid
(the system is more effective than NaBH4–H3BO3) occurs
selectively at room temperature to form the corresponding
benzylamines XVI–XXI in 60-90% yields (Scheme 1).
Quinaldine azomethine XV in these conditions gives the
product of the C=N bond and the quinoline ring reduc-
In order to establish the scope of application of the
techniques we had proposed previously of Schiff bases
reduction into benzylamines with hydrazine hydrate in
the presence of skeletal Raney nickel [6], we investigated
the compounds IX-XII, XIV, XV. At the interaction of
nitro-substituted imines IX, XI, XII with N2H4/Ni-Raney
in methanol-tetrahydrofuran at 20–50°C along with the
212

FUNCTIONALLY SUBSTITUTED SCHIFF BASES
213
Scheme 1.
R
CHO
N
R
H2N
+
MeOOC
MeOOC
IX_XV
I_VII
VIII
NaBH4_AcOH (IX_XV)
_
R
_
N
NaBH4 H3BO3 (IX, XII, XIII)
NaBH4 AcOH
H
MeOOC
CF3
XVI_XXII
CH3
CH3
(IV, XII, XIX),
(II, X, XVII),
O2N
(III, XI, XVIII),
(I, IX,
R =
H3C
XVI),
O2N
CH3
NO2
NO2
N
(VII, XV, XXII).
(V, XIII, XX),
(VI, XIV, XXI),
H3C
N
N
N
N
H
N
Scheme 2.
XVI
Me
H2N 3
NH
1
4
Alloy Al/Ni_KOH
or Ni-Ra, N2H4
2
O2N
COOH
NH
XXIII
COOMe
Me
H2N
XVI, XVIII, XIX
XVIII, XIX
IX
NH
_
COOMe
NaBH4 AcOH
Me
O2N
XXIV, XXV
XXIII
N
Ni-Ra, N2H4
COOMe
XI, XII
Me
IX, XI, XII
XXIV, XXV
2-Me (XI, XII, XVIII, XIX, XXIV, XXV), 4-Mе (IX, XVI); 3-NO2 (IX, XVI), 4-NO2 (XI, XVIII), 5-NO2 (XII, XIX);
-NH2 (XXIV), 5-NH2 (XXV).
reduction of the nitro group the azomethine bond was
hydrogenated, resulting in 58–74% yields of the same
diamines XXIII-XV as at the reduction of nitrobenzyl
derivatives XVI, XVIII, XIX (Scheme 2).
are sensitive to pH of the reaction medium, thus often
products of the hydrogenolysis of the C = N bond
formed, and of the hydrolysis of the ester group. Thus,
the reduction of imine IX with hydrazine hydrate in the
above conditions leads to the formation of acid XXIII.
At the same time, in the molecule of quinolinylimines
XIV, XV the hydrazine hydrate in the presence of
The result of the reduction of azomethines depends
on their structure, on the activity of skeletal catalyst,
and on the temperature of the reaction medium. Imines
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 2 2013

KOROLEVA et al.
214
Scheme 3.
NH2
N
HN
COOMe
Δ
N2H4, Ni-Ra,
+
COOMe
N
R
R
N
R
N
XXI, XXII
XIV, XV
VI, VII
R= H (VI, XIV, XXI), Me (VII, XV, XXII).
the same compounds XXI, XXII as in the reduction with
sodium borohydride at 0–5°C.
Raney nickel reduces the C = N bond, without affecting
the methoxycarbonyl group and the quinoline nucleus:
quinolylaminomethyl benzoates XXI, XXII are formed
in a yield of 37–39% (Scheme 3 ).
The activity of the skeletal catalyst is crucial, since the
reduction of the imine bond competes with the retrode-
composition of the imine under the action of the base. The
decomposition products were observed in the reduction
of imines XIV, XV with the mixture N2H4–Ni Raney at
heating: along with benzyl derivatives XXI, XXII 35%
of aminoquinoline VI, VII was formed (Scheme 3 ).
Reducing imines with a mixture of hydrazine hydrate–
Raney nickel is comparable in the effectiveness with the
reduction of imines with sodium borohydride, but the
former is more selective for quinolylimines since the
reduction of the heterocyclic fragment is not observed.
However, the selective reduction with hydrazine hydrate
requires a high activity of the skeletal catalyst (Ni–Ra).
Direct reduction of imine IX with a mixture of
hydrazine hydrate–Raney nickel at heating (60°C) in
methanol also happened with the splitting of the C=N
bond. 4-Methyl-1,3-phenylenediamine (XXVII) and
4-(hydroxymethyl)benzoate (XXVIII) were isolated
whose structure was established according to IR, mass
spectra and NMR spectra. Reducing the isomeric imine
XII in the system N2H4–Ni Raney occurs selectively to
The products of hydrazine hydrate reduction of imines
IX, XI, XII according to the physicochemical methods
of analysis are identical to diamines XXIII-XXV ob-
tained by the reduction with a mixture N2H4–Ni Raney
of benzylnitroanilines XVI, XVIII, XIX. The hydrazine
hydrate reduction of quinoline imines XIV, XV produced
Scheme 4.
NH2
O2N
R2
R1
XII, H2NNH2, Ni-Ra,
MeOH, 20oC
VIII, EtOH,
Δ
N
XXV or XXIX
O2N
CO2Me
R1
R2
I, IV
IX, XII
VIII, NaBH4_AcOH,
NaBH4_AcOH,
0_5oC
IX, H2NNH2, Ni-Ra,
MeOH,
0_5oC
Δ
O2N
NH2
Me
OH
R2
NH
+
MeO2C
CO2Me
R1
H2N
XXVIII
XVI, XIX
XXVII
H2NNH2, Ni-Ra,
MeOH, 20oC
H2N
R2
H2N
R2
NH
CH3N2
+ XXV, XXX
NH
R1
CO2H
R1
XXIII, XXIX
CO2Me
XXV, XXX
R1 = Me, R2 = H (IV, XII, XIX, XXV, XXIX), R1 = H, R2 = Me (I, IX, XVI, XXIII, XXX).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 2 2013

FUNCTIONALLY SUBSTITUTED SCHIFF BASES
215
Scheme 5.
O2N
N
CO2Me
CF3
X
NaBH4_AcOH
H2NNH2, Ni-Ra,
MeOH,
Δ
NH2
NH2
H2NNH2, Ni-Ra,
MeOH, THF, 20oC
CF3
+
+ XXVIII
H2N
NH
O2N
NH
CF3
COOMe
COOMe
CF3
XXVI
XXXI
XVII
nitrobenzyl derivative XVII into diamine XXVI proceeds
with a low yield (18%) only in the reaction at 0–15°C,
and at 50–60°C the yields of 2-trifluoromethyl-1,4-
phenylenediamine XXXI and alcohol XXVIII reached
70–80% (Scheme 5).
give methoxycarbonyl derivative XXV or carboxy de-
rivative XXIX. The same decomposition was observed
with less active Raney Ni. Perhaps the different ability
to reduction of compounds IX and XII is associated with
different steric accessibility of the C=N bond and nitro
groups in the imine molecule, and therefore in imine IX
the basic hydrolysis occurs followed by the reduction of
the products of primary cleavage to amine XXVII and
alcohol XXVIII (Scheme 4).
The reaction progress was monitored by thin layer
chromatography. The identification of compounds ob-
tained at different stages of transformation of imines was
carried out on the basis of the combination of IR, mass
spectra and 1H and 13C NMR spectra. Analytical param-
eters of the spectral properties of the compounds in the
succession of reactions were the characteristic absorption
bands of imino, amino, nitro, and carbonyl groups in
the IR spectra [ν 1632–1625 (C = N), 3490–3290 (NH),
1537–1520 and 1375–1320 (NO2), 1740–1695 cm–1
In the reaction mixture at heating with hydrazine hy-
drate the hydrolysis of the ester function occurs to form
acids XXIII, XXIX, in which some or all the originally
formed esters XXV, XXX are transformed. The initial
imino-IX, XII and nitrobenzyl esters XVI, XIX can
also be hydrolyzed and then participate in the reduction
reaction in the form of acids. Therefore, the reduction
of compounds IX, XI, XII was carried out under milder
conditions, cooling the reaction mixture at the stage of
mixing the reagents or using reduction first with sodium
borohydride with the release of benzylamine, where
further the nitro group was reduced. Thus, for the syn-
thesis of compounds XXV, XXX first imines IX, XII
were reduced into nitrobenzylamines XVI, XIX with a
mixture of NaBH4–AcOH (or benzylamines XVI, XIX
were obtained by the reductive alkylation of methylni-
troanilines I, IV). Then nitrobenzylamines XVI, XIX
were reduced with hydrazine hydrate in the presence
of skeletal catalyst under mild conditions (no heating)
(Scheme 4). Acids XXIII, XXIX (or their mixture with
esters) were converted to diaminoesters XXV, XXX by
exhaustive methylation with diazomethane (Scheme 4).
1
(CO)], in the H NMR spectra, signals δ 8.50–10.11
(HC=N), 3.38–6.94 (NH and NH2), 4.34–4.77 ppm (CH2),
in the 13C NMR spectra, the signal of methylene C atoms
of benzylamines at δ 47.18–51.67 ppm, the number of
signals corresponding to the number of carbon atoms in
the molecule, in the mass spectra, the presence of the
molecular ion peak.
The compounds obtained due to the presence in the
molecule of functional amino, nitro, carboxy groups
are promising precursors for obtaining substances with
practically useful properties. Carboxy and amino groups
are precursors of the amide bond, causing in many cases
the biological activity of compounds.
EXPERIMENTAL
We failed to select the reduction conditions for trifluo-
romethylimine X to diamine XXVI blocking the cleavage
of the C = N bond in the parent compound, which was
obviously a consequence of mesomeric and inductive
effects of the trifluoromethyl group. The reduction of
IR spectra were taken on a Fourier spectrometer Bruker
Tenzor 27 in the range 400–4000 cm–1. NMR spectra were
registered on a spectrometer Bruker Аvance-500, oper-
ating frequencies 500 (1Н) and 125 MHz (13С). Chemi-
cal shifts are reported in ppm in the δ scale measured
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 2 2013

KOROLEVA et al.
216
from internal reference TMS (0 ppm) in the 1Н spectra,
from СDCl3 (77.0 ppm) or DMSO-d6 (39.43 ppm) in
the 13С spectra. Elemental analysis was performed on
a CHNS analyzer VarioMICRO. Melting points were
in 5 ml of methanol. The reaction mixture was stirred at
60°С for 1 h, filtered when warm through a celite bed, the
filter was washed with methanol, the combined filtrates
were evaporated. The residue was dissolved in 40 ml of
ethyl acetate, the solution was washed with water, dried,
evaporated to 2/3 of its volume, and compound V was
precipitated by hexane. Yield 76%, yellow crystals, mp
160–162°С. IR spectrum (KBr), ν, cm–1: 3440–3360,
1620, 1580. 1Н NMR spectrum (CDCl3), δ, ppm: 2.17 s
(3Н, Mе), 3.69 br.s (2Н, NH2), 6.94 d.d (1Harom, J 8.0,
measured on a Koeffler heating block
.
GLC analysis and recording of mass spectra was car-
ried out on instruments HP 6890/5973, column НР-5MS
30 m × 0.25 mm, 5% PLMe Silicone, and a quadrupol GC-
MS Thermo Scientific Trace GC Ultra/DSQ II with direct
sample admission in the EI mode at the energy 70 eV.
2.1 Hz), 7.03 d (1Harom, J 8.0 Hz), 7.14 d (1Harom
,
The monitoring of the reaction progress and the
checking of the purity of compounds obtained was
performed by TLC on plates Merk DC-Plasticfolien
Kieselgel 60 F254, Sorbfil, in the systems butanol–
ethanol–NH4OH, 8 : 1 : 1; chloroform–methanol, 95 : 5;
ether–hexane, 3 : 1.
J 5.1 Hz), 7.16 d (1Harom, J 2.1 Hz), 7.18 s (1Harom),
7.44 d.d (1Harom, J 7.4, 4.8 Hz), 8.36 d.t (1Harom, J 8.0,
1.8 Hz), 8.50 d (1Harom, J 5.1 Hz), 8.73 d.d (1Harom, J 4.8,
1.8 Hz), 9.29 d (1Н, NH, J 1.8 Hz). 13C NMR spectrum
(CDCl3), δ, ppm: 16.55, 107.66, 109.80, 116.83, 123.34,
130.44, 132.56, 134.17, 137.93, 144.71, 148.33, 151.16,
158.68, 160.24, 162.22. Mass spectrum, m/z (Irel, %): 277
(100) [M]+, 262 (78) [M – Me]+, 121 (9), 77 (5.5). Found,
%: С 69.19; Н 5.35; N 25.04. C16H15N5. Calculated, %:
С 69.31; Н 5.42; N 25.27.
N,N-(4-methylaminophenyl)[4-(pyridin-3-yl)-py-
rimidin-2-yl]amine (V) was obtained by procedure [8].
To 7.04 g (40 mmol) of 3-dimethylamino-1-(3-pyridyl)-
2-propen-1-one in 20 ml of DMF was added 10.0 g
(40 mmol) of 4-methyl-3-nitrophenylguanidine nitrate
and after heating to 50°С was added 17.6 g (44 mmol)
of sodium hydroxide dissolved in a little water. The reac-
tion mixture was heated at 110–130°С for 6 h, cooled,
2-propanol was added and the mixture was left standing
for crystallization. The separated precipitate of N,N-(4-
methyl-3-nitrophenyl)-4-[(pyridyl-3-yl)pyrimidin-2-yl]
amine was filtered off, washed with 2-propanol (2 ×
50 ml). Yield 92%, yellow crystals, mp 200–202°С. IR
spectrum (KBr), ν, cm–1: 3340, 1630, 1580, 1550, 1330.
1Н NMR spectrum (DMSO-d6), δ, ppm: 1.99 s (3Н,
Mе), 6.73 d (1Harom, J 8.4 Hz), 6.86 d (1Harom, J 5.2 Hz),
6.96 d.d (1Harom, J 8.0, 4.8 Hz), 7.35 d.d (1Harom, J 8.4,
2.2 Hz), 7.95 d.t (1Harom, J 8.0, 1.6 Hz), 8.03 d (1Ha-
rom, J 5.2 Hz), 8.12 d.d (1Harom, J 4.8, 1.6 Hz), 8.29 s
(1Harom), 8.74 d (1Harom, J 2.2 Hz), 9.47 br.s (1Н, NH).
13С NMR spectrum (DMSO-d6), δ, ppm: 19.43, 108.22,
114.04, 123.28, 124.59, 132.04, 134.02, 139.56, 148.57,
150.76, 150.97, 152.68, 153.14, 158.74, 159.84, 161.61.
Mass spectrum, m/z (Irel, %): 307 (100) [M]+, 262 (62)
[M – NO2]+, 290 (55) [M – CH3]+, 156 (54), 104 (41), 77
(20). Found, %: С 62.43; Н 4.12; N 22.59. C16H13N5О2.
Calculated, %: С 62.54; Н 4.23; N 22.80.
Characteristics of methyl 4-{[(2-methyl-5-ni-
trophenyl)imino]methyl}benzoate (XII), methyl
4-[(5-quinolinylimino)methyl]benzoate (XIV), methyl
4-{[5-(2-methyl)-quinolinylimino]methyl}benzoate
(XV), methyl 4-[(2-methyl-5-nitroanilino)methyl]benzo-
ate (XIХ), methyl 4-[(5-quinolinylamino)methyl]benzo-
ate (XXI) were given in [6].
Azomethines IX–XI, XIII. General procedure. A
solution of equimolar quantities (10 mmol) of amine I–
III, V and aldehyde VIII in 30 ml of ethanol was boiled
for 10–30 min. The precipitate separated on cooling was
filtered off and recrystallized from a mixture benzene–
ethanol, 1 : 3.
Methyl 4-{[(4-methyl-3-nitrophenyl)imino]
methyl}-benzoate (IX). Yield 85%, light-yellow crystals,
mp 144–145°С. IR spectrum (KBr), ν, cm–1: 3085, 3040,
2964, 1730 (С=О), 1625 (C=N), 1530, 1375 (NO2).
1Н NMR spectrum (CDCl3), δ, ppm: 2.62 s (3Н, Mе),
3.96 s (3Н, ОMе), 7.38 d (1Harom, J 8.1 Hz) 7.41 d.d
(1Нarom, J 8.1, 2.0 Hz), 7.86 d (1Harom, J 2.0 Hz), 7.99 d
(2Harom, J 8.3 Hz), 8.16 d (2Нarom, 8.3 Hz), 8.55 s (1Н,
HС=N). 13C NMR spectrum (CDCl3), δ, ppm: 19.49,
51.74, 115.90, 125.45, 128.23, 129.40, 130.72, 132.23,
132.86, 138.62, 149.52, 159.98, 165.76. Mass spectrum,
m/z (Irel, %): 298 (100) [M]+. Found, %: С 64.28; Н 4.53;
N 9.31. C16H14N2O4. Calculated, %: С 64.43; Н 4.70;
N 9.40.
To a slurry of 4.1 g (15 mmol) of N,N-(4-methyl-3-
nitrophenyl)[4-(pyridin-3-yl)pyrimidin-2-yl]amine in
30 ml of methanol and 3.5 mmol (~0.6 g) of skeletal
Raney nickel was added at heating to °50°С while stir-
ring 5 ml (~5 equiv) of 80% aqueous hydrazine hydrate
Methyl 4-{[4-nitro-2-(trifluoromethyl)phenylimino]
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 2 2013

FUNCTIONALLY SUBSTITUTED SCHIFF BASES
217
methyl}benzoate (X). Yield 90%, light-yellow crystals,
mp 81–82°С. IR spectrum (KBr), ν, cm–1: 3090, 3047,
2970, 1740 (С=О), 1630 (C=N), 1537, 1375 (NO2). 1Н
NMR spectrum (CDCl3), δ, ppm: 3.97 s (3Н, Mе), 6.77 d
(1Harom, J 9.0 Hz), 7.96 d (2Harom, J 8.3 Hz), 8.18 d.d
(1Harom, J 9.0, 2.4 Hz), 8.20 d (2Harom, J 8.3 Hz), 8.40 d
(1Harom, J 8.3 Hz), (7Нarom, 3J 7.9–8.3, 4J 2.4 Hz), 10.11 s
(1Н, НC=N). 13C NMR spectrum (CDCl3), δ, ppm: 52.82,
112.56, 112.81, 116.56, 122.77, 124.37, 124.94, 128.92,
129.76, 130.43, 135.34, 138.43, 139.39, 149.83, 166.31,
191.89. Mass spectrum, m/z (Irel, %): 352 (68) [M]+.
Found, %: N 7.78. C16H11F3N2O4. Calculated, %: N 7.95.
(for azomethine XV at 0–5°С) and was left overnight.
The reaction mixture was diluted with 40–50 ml of
20% aqueous NaOH, The organic layer was separated,
washed with water, and dried with MgSO4. The solvent
was evaporated, the solid residue was recrystallized from
ethanol (XVI–XX) or from a mixture benzene–ethanol,
1:1 (XXI, XXII).
Reductive alkylation of amines I–IV with
4-methoxycarbonylbenzaldehyde (VIII). b. Asolution
of equimolar quantities (10 mmol) of amine I–IV and
aldehyde VIII in 30 ml of benzene was heated at 60°С
for 1–1.5 h, then cooled to room temperature, and the
mixture was poured at stirring to a cooled (0°С) mixture
of 20 mmol of NaBH4, 10 ml of benzene, and 60 mmol of
acetic acid. The obtained mixture was stirred for 30 min
at room temperature, then 6 h at 50°С. Reaction products
XVI–XIX were isolated as described above.
Methyl 4-{[(2-methyl-4-nitrophenyl)imino]methyl}-
benzoate (XI). Yield 64%, mp 202–203°С. IR spectrum
(KBr), ν, cm–1: 3065, 3040, 2970, 2910, 1720 (С=О),
1
1630 (С=N), 1530, 1350 (NO2). Н NMR spectrum
(CDCl3), δ, ppm: 2.43 s (3Н, Mе), 3.98 s (3Н, ОMе),
7.30 d (1Нarom, J 8.1 Hz), 7.75 d (1Нarom, J 8.1 Hz),
8.04 d (1Нarom, J 8.1 Hz), 8.09 d (2Нarom, J 8.1 Hz),
8.22 d (2Нarom, J 8.1 Hz), 8.50 s (1Н, НС=N). 13C NMR
spectrum (CDCl3), δ, ppm: 18.23, 52.69, 118.05, 118.41,
122.98, 125.76, 129.24, 130.35, 133.37, 139.40, 145.77,
156.59, 160.68, 166.62. Mass spectrum, m/z (Irel, %):
298 (100) [M]+. Found, %: С 64.35; Н 4.59; N 9.29.
C16H14N2O4. Calculated, %: С 64.43; Н 4.70; N 9.40.
Methyl 4-[(4-methyl-3-nitrophenylamino)methyl]
benzoate (XVI). Yield 90% (а), 80% (b), yellow
crystals, mp 107–108°С. IR spectrum (KBr), ν, cm–1:
3440 (NH), 1740 (С=О), 1520, 1360 (NO2), 1300,
1
1120. Н NMR spectrum (CDCl3), δ, ppm: 2.44 s (3Н,
Mе), 3.91 s (3Н, ОMе), 4.36 br.s (1Н, NH), 4.42 с (2Н,
СН2), 6.70 d.d (1Harom, J 8.3, 2.5 Hz), 7.08 d (1Harom
J 7.4 Hz), 7.20 d (1Harom, J 2.5 Hz), 7.41 d (2Harom
,
,
J 7.3 Hz), 8.01 d (2Harom, J 7.3 Hz). 13C NMR spectrum
(CDCl3), δ, ppm: 19.69, 48.11, 52.33, 108.21, 118.04,
122.34, 127.36, 129.74, 130.35, 133.59, 143.92, 146.73,
150.03, 167.02. Mass spectrum, m/z (Irel, %): 300 (100)
[M]+. Found, %: С 63.89; Н 5.14; N 9.25. C16H16N2O4.
Calculated, %: С 64.00; Н 5.33; N 9.33.
Methyl 4-({2-methyl-5-[4-(pyridin-3-yl)pyrimidin-
2-ylamino]phenylimino}methyl)benzoate (XIII). Yield
80%, yellow crystals, mp 193–194°С. IR spectrum (KBr),
ν, cm–1: 3410 (NH), 3040, 2970, 2910, 1725 (С=О), 1632
(С=N). 1Н NMR spectrum (CDCl3), δ, ppm: 2.36 s (3Н,
Mе), 3.96 s (3Н, ОMе), 7.18 d (1Нarom, J 4.9 Hz), 7.23 d
(1Нarom, J 8.9 Hz), 7.35 с (1Нarom), 7.40 m (2Нarom),
Methyl 4-{[4-nitro-2-(trifluoromethyl)phenyl-
amino]methyl}benzoate (XVII). Yield 60% (а), 55% (б),
yellow oily fluid. IR spectrum (film), ν, cm–1: 3450 (NH),
7.52 s (1Нarom), 8.04 d (2Нarom, J 8.1 Hz), 8.15 d (2Нarom
,
J 8.1 Hz), 8.35 d (1Нarom, J 7.8 Hz), 8.51 s (1H, НC=N),
8.52 d (1Нarom, J 4.9 Hz), 8.73 d (1Нarom, J 4.5 Hz), 9.30 s
(1Н, NH). 13С NMR spectrum (CDCl3), δ, ppm: 17.00,
29.42, 52.07, 107.93, 108.73, 117.05, 123.33, 126.55,
128.40, 129.71, 130.39, 131.98, 132.50, 134.12, 137.70,
139.94, 148.33, 150.51, 151.28, 158.10, 158.81, 160.13,
162.25, 166.38. Mass spectrum, m/z (Irel, %): 423 (82)
[M]+. Found, %: С 70.83; Н 4.79; N 16.37. C25H21N5O2.
Calculated, %: С 70.92; Н 4.96; N 16.55.
1
1720 (C=O), 1620, 1520, 1350 (NO2), 1130. Н NMR
spectrum (CDCl3), δ, ppm: 3.90 s (3Н, ОMе), 4.77 s (2Н,
СН2), 4.90 br.s (1Н, NH), 6.76 d (1Harom, J 9.0 Hz), 7.43 d
(2Harom, J 8.2 Hz), 8.02 d (2Harom, J 8.2 Hz), 8.17 d.d
(1Harom, J 9.0, 2.3 Hz), 8.39 d (1Harom, J 2.3 Hz). 13С
(CDCl3), δ, ppm: 51.67, 64.23, 115.89, 122.10, 123.70,
123.74, 126.02, 128.23, 128.86, 129.39, 138.49, 145.57,
149.23, 166.56. Mass spectrum, m/z (Irel, %): 354 (88) [M]+.
Found, %: N 7.75. C16H13F3N2O4. Calculated, %: N 7.91.
Reduction of azomethines IX–XV with sodium
borohydride. а. A solution or a slurry of 10 mmol of
azomethine IX–XV in 30 ml of benzene was added at
stirring to a cooled to 0°С mixture of 20 mmol of NaBH4,
10 ml of benzene, and 60 mmol of glacial acetic acid. The
reaction mixture was stirred for 6 h at room temperature
Methyl 4-[(2-methyl-4-nitrophenylamino)methyl]
benzoate (XVIII). Yield 88% (а), 79% (b), mp 182–
183°С. IR spectrum (KBr), ν, cm–1: 3410 (NH), 1735
(С=О), 1525, 1355 (NO2), 1320, 1100. 1Н NMR spectrum
(CDCl3), δ, ppm: 2.25 s (3Н, Mе), 3.92 s (3Н, ОMе),
4.57 d (2Н, СН2, 3J 3.9 Hz), 4.72 br.s (1Н, NH), 6.47 d
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KOROLEVA et al.
218
product was additionally extracted with ethyl acetate.
The combined filtrate was evaporated. The residue
was diluted in dichloromethane at heating, filtered, the
filtrate was washed with water and dried with Na2SO4.
On evaporating the solvent to 2/3 of the initial volume
the product was precipitated with petroleum ether. The
obtained compounds XXIV, XXV were materially pure
according to TLC data.
(2Нarom, J 8.2 Hz), 7.40 d (1Нarom, J 8.2 Hz), 8.00 d
(2Нarom, J 8.2 Hz), 8.05 d (2Нarom, J 8.2 Hz). 13C NMR
spectrum (CDCl3), δ, ppm: 17.13, 47.18, 51.95, 108.17,
121.00, 124.29, 125.86, 126.73, 129.48, 130.00, 137.90,
142.48, 121.90, 150.68, 166.40. Mass spectrum, m/z (Irel,
%): 300 (100) [M]+. Found, %: С 63.75; Н 5.23; N 9.20.
C16H16N2O4. Calculated, %: С 64.00; Н 5.33; N 9.33.
Methyl 4-(2-methyl-3-{5-[4-(pyridin-3-yl)pyrimi-
din-2-ylamino]phenylamino}methyl)benzoate (XХ).
Yield 73% (а), yellow crystals, mp 107–108°С. IR spec-
trum (KBr), ν, cm–1: 3410 (NH), 3340 (NH), 3040, 2924,
Reduction of imines IX–XII, XIV, XV and nitro-
substituted amines XVI–XIX with hydrazine hydrate
in the presence of Raney nickel. d. To a solution of
10 mmol of imine IX–XII, XIV, XV or amine XVI–XIX
in 30 ml of a mixture methanol–THT, 1 : 1, was added
0.06 g of crude Ni–Ra, then 40 mmol of 80% water so-
lution of hydrazine hydrate in 1 ml of methanol (at the
synthesis of aminoester ХХХ from imine IX and nitro-
benzylaminocarboxylate XVI and of ester XXV from
imine XII the hydrazine hydrate was added at cooling the
mixture to 0–5°С). The foam formation and discoloration
of the reaction mixture was observed. The mixture was
stirred for 15 min at 50–60°С (at the synthesis of esters
XXV, XXX at 20°С), then 1 h at room temperature, the
mixture was filtered through a celite bed, the filtrate was
evaporated. At the reduction of imines XIV, XV the resi-
due was boiled with water to remove the amine VI, VII.
The solid product was dried, compounds XXIII–XXVI,
XXIX, XXX were purified by dissolving in toluene or
ethyl acetate and precipitation with hexane, quinolinyl-
amines XXI, XXII were recrystallized from a mixture
benzene–ethanol, 1:1.
1
2853, 1710 (С=О), 1620. Н NMR spectrum (CDCl3),
δ, ppm: 2.19 s (3H, Me), 3.90 s (3H, OMe), 4.07 br.s
(1H, NH), 4.51 d (2H, СН2, J 5.3 Hz), 6.86 s (1Нarom),
6.94 s (1Нarom), 7.08 s (1Нarom), 7.11 d (1Нarom), 7.39 d.d
(1Harom, J 7.2, 4.8 Hz), 7.45 d (2Нarom, J 7.3 Hz), 7.58 d.d
(1Нarom, J 8.0, 5.7 Hz), 7.99 d (2Нarom, J 7.3 Hz), 8.47 d
(1Нarom, J 5.1 Hz), 8.52 d (1Нarom, J 8.0 Hz), 8.67 d
(1Нarom, J 5.6 Hz), 9.25 s (1H, NH). 13С NMR spectrum
(CDCl3), δ, ppm: 17.27, 48.24, 52.34, 102.31, 107.86,
108.88, 123.87, 127.58, 129.79, 130.00, 131.81, 132.82,
134.11, 141.17, 143.51, 146.64, 147.91, 149.72, 150.18,
157.55, 159.30, 165.98, 167.45. Mass spectrum, m/z (Irel,
%): 425 (100) [M]+. Found, %: С 70.42; Н 5.25; N 16.13.
C25H23N5O2. Calculated, %: С 70.59; Н 5.41; N 16.47.
Methyl 4-{[5-(2-methyl)quinolinylamino]methyl}
benzoate (XXII). Yield 76% (а), mp 94°С. IR spectrum
(KBr), ν, cm–1: 3442 (NH), 3245, 2920, 2835, 1720
1
(C=O), 1620, 1596, 1434, 1274. Н NMR spectrum
(CDCl3), δ, ppm: 2.72 s (3Н, Mе), 3.91 s (3Н, ОMе),
4.54 d (2Н, СН2, J 3.8 Hz), 4.81 br.s (1Н, NH), 6.51 d
Methyl 4-[(5-quinolinylamino)methyl]benzoate
(XXI). Yield 39% from imine (XIV) (d), light-brown
crystals, mp 109°С (108–109oC [6]).
(1Harom, J 7.2 Hz), 7.16 m (1Harom), 7.25 d.d (1Harom
,
J 7.2, 4.2 Hz), 7.43 m (2Harom), 7.48 d (2Harom, J 8.1 Hz),
8.02 d (2Harom, J 8.1 Hz). 13С NMR spectrum (CDCl3),
δ, ppm: 25.12, 48.18, 52.08, 104.74, 116.51, 118.46,
120.27, 127.28, 128.77, 129.32, 130.02, 130.19, 142.94,
144.07, 148.80, 158.58, 166.82. Mass spectrum, m/z (Irel,
%): 306 (100) [M]+. Found, %: С 74.28; Н 5.79; N 8.97.
C19H18N2O2. Calculated, %: С 74.51; Н 5.88; N 9.15.
Methyl 4-{[5-(2-methyl)quinolinylamino]methyl}
benzoate (XXII). Yield 37% from imine XV (d). Char-
acteristics of the compound, see procedure а.
4-[(3-Amino-4-methylphenylamino)methyl]ben-
zoic acid (XXIII). Yield 65% from imine IX (d), 62%
from nitroamine XVI, white crystals, mp 139–140°С. IR
spectrum (KBr), ν, cm–1: 3370–3350 (NH, NH2, ОН),
The reduction of nitro-substituted benzylamines
XVIII, XIX with Raney alloy in the presence of KОН.
c. To the heated to 55°С slurry of 2 g (6.5 mmol) of nitro
compound XVIII, XIX and 0.5 g of Raney alloy in 40 ml
of methanol was poured 40 ml of 1.5 M water solution
of KOH, and the mixture was stirred at 45–55°С for
30–40 min till complete conversion of the initial nitro
compound (TLC monitoring). The hot reaction mixture
was filtered through a celite bed, the filter was washed
with methanol, and from the Raney alloy the reaction
1
1695 (С=О), 1620, 1520. Н NMR spectrum (D2O), δ,
ppm: 2.05 s (3Н, Mе), 4.01 br.s (2Н, NН2), 4.34 s (2Н,
CH2), 5.95 d (1Harom, J 2.3 Hz), 6.02 d.d (1Harom, J 8.1,
2.3 Hz), 6.81 d (1Harom, J 8.1 Hz), 6.94 br.s (1Н, NH),
7.41 d (2Harom, J 8.3 Hz), 7.69 d (2Harom, J 8.3 Hz).
13С NMR spectrum (D2O), δ, ppm: 16.620, 48.27, 99.97,
104.18, 112.45, 127.38, 127.62, 131.34, 144.56, 145.53,
147.43, 168.76, 171.16. Mass spectrum, m/z (Irel, %):
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 2 2013

FUNCTIONALLY SUBSTITUTED SCHIFF BASES
219
256 (10) [M]+, 255 (75) [M – 1]+, 135 (20), 121 (100)
lized from a mixture ethyl acetate–ethyl ether, 1 : 1.
[C6H5CO2]+. Found, %: С 70.19; Н 6.10; N 10.74.
C15H16N2O2. Calculated, %: С 70.31; Н 6.25; N 10.94.
4-Methyl-1,3-phenylenediamine (XXVII). Yield 45%,
mp 98–99°С (from ethanol). IR spectrum (KBr), ν, cm–1:
3400, 3355, 3310 (NH2). 1Н NMR spectrum (CD3OD), δ,
ppm: 2.06 s (3Н, Mе), 3.48 br.s (4Н, NН2), 6.06 s (1Ha-
rom), 6.09 d (1Harom, J 8.0 Hz), 6.82 d (1Нarom, J 8.0 Hz).
13С NMR spectrum (CD3OD), δ, ppm: 16.17, 101.84,
105.69, 112.59, 130.79, 144.95, 145.18. Mass spectrum,
m/z (Irel, %): 122 (94) [M]+. Found, %: С 68.71; Н 8.05;
N 22.73. C7H10N2. Calculated, %: С 68.85; Н 8.20;
N 22.95.
Methyl 4-[(4-amino-2-methylphenylamino)methyl]
benzoate (XXIV). Yield by procedure c 51%; by proce-
dure d 58% from imine XI, 63% from nitroamine XVIII,
yellow crystals, mp 144–145°С. IR spectrum (KBr), ν,
cm–1: 3463, 3440, 3385 (NH, NH2), 3065, 3035, 2930,
1710 (С=О), 1330, 1115. 1Н NMR spectrum (DMSO-d6),
δ, ppm: 2.05 s (3Н, Mе), 3.38 br.s (2Н, NН2), 3.90 s (3Н,
ОMе), 4.48 s (2Н, CH2), 5.22 d (1Нarom, J 8.2 Hz), 6.47
d.d (2Нarom, J 8.2, 2.4 Hz), 7.77 d (2Нarom, J 8.0 Hz),
7.92 d (2Нarom, J 8.0 Hz), 8.46 s (1Н, NН). 13С NMR spec-
trum (DMSO-d6), δ, ppm: 19.58, 46.84, 51.20, 114.23,
114.95, 116.29, 126.19, 126.67, 127.19, 129.7, 131.95,
135.93, 146.13, 145.82, 146.74, 167.91. Mass spectrum,
m/z (Irel, %): 270 (73) [M]+. Mass spectrum, m/z (Irel,
%): 270 (73) [M]+. Found, %: С 70.98; Н 6.45; N 10.23.
C16H18N2O2. Calculated, %: С 71.11; Н 6.67; N 10.37.
Methyl 4-(hydroxymethyl)benzoate (XXVIII).
Yield 40%, white crystals, mp 47–50°С. IR spectrum
(film), ν, cm–1: 3500, 2950, 1721, 1613, 1590, 1415.
1Н NMR spectrum (CDCl3), δ, ppm: 3.88 s (3Н, ОMе),
4.71 s (2Н, СН2), 2.54 br.s (1Н, ОН), 7.39 d (2Нarom
,
J 8.0 Hz), 7.99 d (2Нarom, J 8.0 Hz). 13С NMR spectrum
(CDCl3), δ, ppm: 51.82, 64.24, 126.14, 129.49, 145.83,
166.76. Mass spectrum, m/z (Irel, %): 166 (100) [M]+.
Found, %: С 64.89; Н 5.95. C9H10О3. Calculated, %:
С 65.06; Н 6.02.
Methyl 4-[(5-amino-2-methylphenylamino)methyl]
benzoate (XXV). Yield 51% (c), 74% (d) from imine XII,
80% from nitroamine XIX. Characteristics of compound
XXV are given in [6].
4-[(5-Amino-2-methylphenylamino)methyl]ben-
zoic acid (XXIX). Yield 63% (d) from imine XII, light-
brown crystals, mp 119–120°С. IR spectrum (KBr), ν,
cm–1: 3420–3390 (NH, ОН), 1710 (С=О), 1610, 1540,
1290. 1Н NMR spectrum (D2O), δ, ppm: 2.05 s (3Н, Mе),
Methyl 4-[(4-amino-2-trifluoromethylphenylamino)
methyl]benzoate (XXVI). Yield 18% (d) from ni-
troamine XVII, light-violet crystals, mp 134–135°С. IR
spectrum (KBr), ν, cm–1: 3490–3310 (NH, NH2), 3055,
2970, 1725 (С=О), 1615. 1Н NMR spectrum (DMSO-d6),
δ, ppm: 3.90 s (3Н, MеO), 4.73 s (2Н, CH2), 4.78 br.s
3.50 br.s (2Н, NH2), 4.34 s (2Н, CH2), 5.95 d (1Нarom
J 8.2 Hz), 6.02 d.d (1Нarom, J 8.3, 2.3 Hz), 6.82 d (1Нarom
,
,
J 8.3 Hz), 6.90 br.s (1Н, NH), 7.41 d (2Нarom, J 8.1 Hz),
7.98 d (2Нarom, J 8.1 Hz). 13С NMR spectrum (D2O),
δ, ppm: 16.65, 47.86, 97.97, 104.2, 112.363, 127.03,
128.99, 129.93, 130.70, 145.04, 145.70, 146.46, 166.94.
Mass spectrum, m/z (Irel, %): 256 (17) [M]+, 255 (55)
[M – 1]+, 121 (100) [C6H5CO2]+. Found, %: С 70.19;
Н 6.10; N 10.74. C15H16N2O2. Calculated, %: С 70.31;
Н 6.25; N 10.94.
(2Н, NH2), 6.17 d (1Harom, J 8.1 Hz), 6.27 d.d (1Harom
J 8.1, 2.3 Hz), 6.49 s (1Harom), 6.86 br.s (1Н, NH), 7.40 d
(2Harom, J 8.1 Hz), 8.00 d (2Harom, J 8.1 Hz) (7Н, Нarom
,
,
3J 8.1, 4J 2.3 Hz). Mass spectrum, m/z (Irel, %): 324 (37)
[M]+. Found, %: N 8.45. C16H15F3N2O2. Calculated, %:
N 8.64.
4-Methyl-1,3-phenylenediamine (XXVII) and
methyl 4-(hydroxymethyl)benzoate (XXVIII) [reduc-
tion of imine IX at 50–60°С (d)[. After the addition of
4 equiv of hydrazine hydrate the mixture was stirred for
1 h at room temperature, filtered through a celite bed, the
filter was washed with methanol, the combined filtrate
was evaporated in a vacuum. To the residue 50 ml of
water was added, the white precipitate of benzyl alcohol
XXVIII was filtered off, washed with water (2 × 30 ml).
The water solutions were extracted with ethyl acetate (3 ×
35 ml). The combined extract was dried with Na2SO4, the
solvent was evaporated in a vacuum, the solid residue of
4-methyl-1,3-phenylenediamine (XXVII) was recrystal-
Methyl 4-[(3-amino-4-methylphenylamino)methyl]
benzoate (XXX). Yield 62% (d) from imine XII, 72%
from nitroamine XIX, light-brown crystals, mp 167–
168°С. IR spectrum (KBr), ν, cm–1: 3410, 3360, 3290
1
(NH, NH2), 1725 (С=О), 1620, 1520, 1240. Н NMR
spectrum (CDCl3), δ, ppm: 2.04 s (3Н, Mе), 3.60 br.s
(2Н, NН2), 3.90 (3Н, ОMе), 4.34 s (2Н, CH2), 4.86 br.s
(1Н, NH), 6.01, d.d (1Нarom, J 8.1, 2.2 Hz), 6.84 d
(1Нarom, J 8.2 Hz), 7.45 d (1Нarom, J 8.2 Hz), 7.70 d
(2Нarom, J 8.0 Hz), 7.89 d (2Нarom, J 8.0 Hz). 13С NMR
spectrum (CDCl3), δ, ppm: 16.60, 48.43, 52.28, 99.99,
104.16, 112.44, 127.30, 130.12, 131.34, 144.55, 145.65,
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KOROLEVA et al.
220
147.49, 167.22. Mass spectrum, m/z (Irel, %): 270 (100)
[M]+. Found, %: С 71.03; Н 6.50; N 10.19. C16H18N2O2.
Calculated, %: С 71.11; Н 6.67; N 10.37.
(30–35°С) for 5–6 h. On the completion of the reaction
(TLC monitoring) the solvent was evaporated, and the
residue was recrystallized from a mixture chloroform–
hexane. Yield 75% (XXV), 80% (XXX).
2-Trifluoromethyl-1,4-phenylenediamine (XXXI).
Yield 75% from imine X (reduction at 50–60°С (d), mp
57–58°С (from benzene). IR spectrum (KBr), ν, cm–1:
3380, 3345, 3275 (NH2). 1Н NMR spectrum (CD3OD),
δ, ppm: 5.59 br.s (4Н, NН2), 6.19 d (1Нarom, J 8.1 Hz),
6.28 d (1Нarom, J 8.1 Hz), 6.55 s (1Нarom). 13С NMR spec-
trum (CD3OD), δ, ppm: 112.19, 116.20, 118.25, 119.11,
120.48, 132.02, 139.10. Mass spectrum, m/z (Irel, %): 176
(100) [M]+. Found, %: N 15.80. C7H7F3N2. Calculated,
%: N 15.91.
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